Diagnosis of common blood stream infection pathogens based on central homo-sequence primer by multiplex PCR combined with MALDI-TOF MS / 中华检验医学杂志

ABSTRACT

Objective:Based on the high-throughput detection technique of multiplex PCR combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, constructing the characteristic SNP profiles of different strains, and establishing a rapid, accurate and highly sensitive method for the diagnosis of bloodstream infection pathogens.Methods:Seven kinds of pathogens such as common Escherichia coli were selected as target. The multiple PCR reaction conditions was optimized, and the characteristic peaks of each target bacteria were detected by MALDI-TOF MS to establish the joint detect system. Common primer pairs and central homo-sequence primer pairs were designed to analyse the formation of primer dimer. Using simulated bacterial infection blood samples with detection system to determine specificity and sensitivity. One hundred and fifty blood samples from suspected bacteremia patients were collected from June to September 2020 in a hospital in Beijing, and the identification results were compared to traditional identification method of clinical application that are using χ 2 test. Results:The cycle threshold (Ct) value of the central homo-sequence primers that were designed were more than 38, with a delay of 6-10 cycles. The joint mass spectrometry detection system could detect seven kinds of bacteria divided into two groups at the same time. The target bacteria can be detected specific product of the peak, and the clinical strains other than the target strains only had primer peaks. All maps had non-specific miscellaneous peaks. The sensitivity of Escherichia coli could reach 50 CFU/ml, and the detection limit of other bacteria was 100 CFU/ml. The detection results of 150 patients showed that 46 cases were positive by traditional method. The positive rate was 30.67% (46/150), including two cases of mixed infection. Forty-eight cases were positive by mass spectrometry, and the positive rate was 32.0% (48/150), including three cases of mixed infections. The negative coincidence rate was 100% (101/101). The comparison of the two methods showed that the P=0.625>0.01, the Kappa=0.938, the sensitivity and specificity was 97.82%(45/46) and 97.11%(101/104), respectively. There was no significant difference between the two methods, and the results of nucleic acid mass spectrometry could also be used in clinic. Conclusions:The established detection system can not only quickly and accurately detect seven common pathogens causing bloodstream infection, and effectively shorten the time needed for traditional culture and identification, but also can detect multiple bacterial mixed infections at the same time to make up for the possibility of missed detection. Besides, the method can also be used to identify other bacteria.